WDPN31 PGTW 110300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEPARTAK)// 
WARNING NR 11//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TROPICAL STORM (TS) NEPARTAK HAS REMAINED QUASI-STATIONARY AND
MAINTAINED ITS INTENSITY OVER THE PAST 12 HOURS. ANIMATED WATER VAPOR
IMAGERY INDICATES THE SYSTEM IS GETTING ELONGATED AS THE NORTHERN EDGE
OF THE STORM IS EXPOSED TO STRONG WESTERLY VERTICAL WIND SHEAR (VWS)
ASSOCIATED WITH THE SUBTROPICAL JET STREAM. THE CURRENT INTENSITY IS
BASED ON DVORAK ESTIMATES FROM PGTW, RJTD, AND KNES. THE CURRENT
POSITION IS BASED ON ANIMATED MULTISPECTRAL IMAGERY AND A 102153
SSMIS MICROWAVE PASS WITH FAIR CONFIDENCE. TS 21W IS VERY SLOWLY
TRACKING ALONG THE WESTERN EDGE OF THE LOW- TO MID-LEVEL STEERING
RIDGE TO THE EAST.
3. FORECAST REASONING.
    A. THE FORECAST PHILOSOPHY HAS CHANGED SLIGHTLY SINCE THE PREVIOUS
BULLETIN TO REFLECT A SLOWER POLEWARD PROGRESSION AND DISSIPATION AT
TAU 72.
    B.  TS 21W IS EXPECTED TO CONTINUE SLOWLY TRACKING NORTH AND
MAINTAIN A MINIMAL TROPICAL STORM INTENSITY AS IT APPROACHES THE JET 
STREAM TO THE NORTH THAT IS MOMENTARILY PROVIDING POLEWARD OUTFLOW.
HOWEVER, THE STRONGER VWS WILL ULTIMATELY ERODE THE SYSTEM AND CAUSE
IT TO DISSIPATE BY TAU 72. THE AVAILABLE NUMERIC GUIDANCE IS IN BETTER
AGREEMENT WITH THE TRACK DIRECTION, HOWEVER, SPEED VARIATIONS REMAIN
WITH WBAR THE FASTEST. THIS FORECAST IS SLOWER AND TO THE LEFT OF
CONSENSUS.//
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